DIPHTHERIA is an acute contagious disease which, on account of its pre valence, its gravity, its consequences, and the frequency with which it is met with in the child, takes a prominent place amongst the disorders of early life. The disease induces great anaemia and prostration, and is characterized anatomically by inflammation of various mucous surfaces and the formation on them of a more or less tough and leathery false mem brane. The inflammation often spreads to some distance from its point of origin, but at first is usually confined to a comparatively limited area. The seat varies in different cases ; and the symptoms are therefore subject to great variety according to the part in which the chief local expression of the disease occurs.
When the inflammatory process attacks the larynx the malady is called membranous croup, and this was long held to be a distinct affection. Whether all cases of membranous croup are diphtheritic in their nature —whether a false membrane can be developed in the air-passages apart from the diphtheritic poison—is a question upon which pathologists in this country are still divided. That membranous croup arises in many cases from this cause is undeniable. Instances have been met with in which diph theria has attacked the pharynx in some members of a family and the larynx in others. Thus, Dr. Woodman found membranous laryngitis in two infants, aged respectively eighteen months and two months, while others of the family suffered from false membrane in the mouth and pharynx. Wilks has seen in different inmates of the same house the disease remain confined to the throat, or spread thence to the larynx, or begin in the larynx ; and Trousseau refers to a case reported by Dr. A. Guerard in which a little girl died of laryngeal croup, and other members of the family suffered immediately afterwards from pseudo-membranous pharyngitis. Moreover, it is admitted by the best authorities that the laryngeal false membrane has exactly the same anatomical characters, whether it be clue to the spread of a pharyngeal diphtheria or arise pri marily as a case of membranous croup.
Advocates of the essential difference between the two forms of illness maintain that the character of the two diseases is not the same. Croup, they say, is a sthenic disease, while diphtheria is asthenic. But some
cases of croup are accompanied by severe constitutional depression and all the signs of profound general disease ; while diphtheria is not invariably accompanied by symptoms of prostration. Indeed, one of the peculiari ties of this affection is the occurrence sometimes of marked paralysis after an attack of sore throat so mild as to be almost overlooked.
Secondly, it is pointed out that in diphtheria the glands at the angles of the jaw are invariably enlarged, while in membranous croup they are little if at all affected. But the larynx has little connection with the su perficial cervical glands. As Dr. Morell Mackenzie has pointed out, in cancer of the larynx the cervical glands are not enlarged, while if the malignant disease affect the pharynx these glands are always involved.
Thirdly, the contagiousness of diphtheria is insisted upon, while mem branous croup is said not to be communicable by one child to another. But the risk of infection is in direct proportion to the amount of exuda tion, and the readiness with which the membrane can be detached and dispersed. In the glottis the membrane is very firmly adherent ; in the pharynx its connections are much looser, and it is much more easily separable from the mucous surfaces. Moreover, as Sir Jenner has observed, the conditions in which the patient is placed vary greatly in the two cases. A child with diphtheria in its early stage is up and about, kisses his brothers and sisters, and has every opportunity of conveying the dis ease to them. A patient with membranous croup is kept in bed apart from the other children and carefully tended. Still, there is strong evidence that, in spite of these hindrances to its ready communication, membranous croup may be conveyed from one child to another. Dr. Trend states that he has seen the laL,y.ugeal disease in more than one child of a family at the same time. Dr. Wilks believes that he has seen diphtheria begin in the house as a case of supposed membranous croup, and afterwards attack others of the inmates in the form of diphtheritic pharyngitis. Dr. A. Guerarcl's case, already referred to, is another instance of the contagious ness and interchangeability of the two varieties.